Lightware SF10 User manual

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SF10
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Laser altimeter Product manual
SF10 Laser Altimeter - Product Manual - Revision 11 of © LightWare Optoelectronics (Pty) Ltd, 20161 15
The SF10 is a compact, lightweight
laser altimeter for above-ground-
level altitude measurement from
small fixed wing or multi-rotor craft.
The SF10 laser altimeter is ideal for
automated landings and precision
hovering.
The configurable features and
multiple hardware interfaces make
the SF10 easy to use with different
types of flight controller.
The SF10 laser altimeter uses a time-
of-flight system to make accurate
distance measurements to natural or
artificial surfaces.
Features:
•Very compact and lightweight - 35 grams.
•Accurate AGL altitude measurement on most
natural and artificial surfaces.
•Fast update rate.
•Includes serial, I2C, USB and analog interfaces
with programmable capabilities.
•Easy to configure using the built-in menu and
LightWare Terminal software.
•Fully calibrated and ready to run.
•Accurate, reliable altitude measurements in
sunlight or dark conditions.
•
Not affected by: speed; wind; changes in
barometric pressure; noise; ambient light; terrain
or air temperature.

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Table of contents
Table of figures
Figure 1 :: The main features of the SF10 3................................................................................................................
Figure 2 :: Applications 4.....................................................................................................................................
Figure 3 :: Power from the USB port 6.....................................................................................................................
Figure 4 :: Regulated +5 V DC power supply connections 6..............................................................................................
Figure 5 :: USB communications 6...........................................................................................................................
Figure 6 :: Analog voltage connections 7...................................................................................................................
Figure 7 :: Serial interface connections 7..................................................................................................................
Figure 8 :: I2C interface connections 7.....................................................................................................................
Figure 9 :: LightWare Terminal showing menu options 8.................................................................................................
Figure 10 :: Altitude represented by distance (Serial / I2C) and analog voltage 9...................................................................
Figure 11 :: Labelling on the SF10 10........................................................................................................................
Figure 12 :: Dimension drawings of the SF10 11...........................................................................................................
Product ordering codes
Disclaimer
Information found in this document is used entirely at the reader’s own risk and whilst every effort has been made to
ensure its validity neither LightWare Optoelectronics (Pty) Ltd nor its representatives make any warranties with respect the
accuracy of the information contained herein.
Product ordering codes 2.....................................................................................................................................
1. Overview 3...................................................................................................................................................
2. Quick start guide 5.........................................................................................................................................
3. Making connections to the SF10 6........................................................................................................................
4. Menu options 8..............................................................................................................................................
5. Instructions for safe use 10...............................................................................................................................
Appendix A :: Specifications 11..............................................................................................................................
Appendix B :: Dimensions 11.................................................................................................................................
Appendix C :: Main cable type 1, 35 cm 12................................................................................................................
Appendix D :: Connecting to Pixhawk Autopilot using “serial 4” 13....................................................................................
Appendix E :: Electromagnetic interference (EMI) graphs 13............................................................................................
Revision history 15.............................................................................................................................................
Model family Model name Model description
SF10 SF10/A (25 m) Laser altimeter, max 25 m
SF10 SF10/B (50 m) Laser altimeter, max 50 m
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1. Overview
The light-weight, SF10 laser altimeter is an essential addition to any scale aircraft that needs fast, accurate and reliable AGL altitude
measurements.
Operating from a regulated 5 V DC supply, the SF10 includes both analog and digital interfaces that can be easily connected to a
flight controller or a standard processing platform. Each interface on the SF10 can be configured using a simple software menu that
is accessible through the built-in, micro USB port.
The SF10 works by measuring the time it takes for a very short flash of laser light to travel to the ground and back again. The
accuracy of the measurement is not affected by the colour or texture of the ground nor the angle of incidence of the laser beam.
The SF10 is virtually immune to background light, wind and noise making it the ideal AGL altimeter for all kinds of terrain.
Figure 1 :: The main features of the SF10
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The maximum operating altitude of the SF10 depends on the model: the SF10/A maximum range is 25 meters; the SF10/B maximum
range is 50 meters; the SF10/C maximum range is 100 meters. Readings are updated 32 times per second in the SF10/A and SF10/B
models, and updated 16 times per second in the SF10/C. There is a filter setting to reduce any unwanted variability in the altitude
introduced by uneven terrain, bushes or long grass.
Figure 2 :: Applications
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2. Quick start guide
1. CAUTION - The SF10 laser altimeter contains a laser and should never be
aimed at a person or an animal. Do not look at the beam directly with
optical instruments.
2. Download LightWare Terminal software from www.lightware.co.za > Library
> Documents > Software onto your PC. Open the installer package and
follow the installation instructions. Everything needed for communicating
with the SF10 will automatically be installed.
3. Plug the “micro-B to type A” USB cable provided into the SF10’s micro USB
connector and connect the other end to your PC. This provides both power
and communication to the unit.
4. Start the LightWare Terminal software and click the “Connect” icon to
open a communications port.
5. If the connection isn’t made automatically, click the “Laser” icon and
select the correct USB port from the list shown.
6. Press the <SPACE> key to display the main menu. This menu includes a list
of all the settings that can be changed in the SF10. A summary of the
settings is given below:
7. Once you have confirmed your settings, press the <SPACE> key to start taking distance measurements and the results
will be displayed in the Terminal window.
8. Press the “Disconnect” icon before unplugging the USB cable.
9. There are several interface options available on the main connector. These connections are used to integrate the SF10
into your system and details of all the options are explained later in this document.
Setting Range of values Description
a: Zero datum offset -10.00 m … +10.00 m Adjusts the zero point from which measurements
are taken
b: Smooth output ON / OFF Switch on filtering to smooth the outputs
c: Serial port baud rate 9600 … 115200 Sets the baud rate for the serial port
d: I2C bus address 0 … 7F Sets the I2C address
e: Analog distance range
SF10/A: 1.00 m … 30.00 m
Sets the distance at which the voltage output will
show 2.56 V
SF10/B: 1.00 m … 60.00 m
SF10/C: 1.00 m … 120.00 m
f: Analog voltage range 0.00 V … 2.56 V or
0.00 V … 3.30 V
Selects the maximum output voltage of the analog
output: either 2.56 V or 3.30 V
g: Analog polarity 0.00 m = 0.00 V | 25.60 m = 2.56 V or
25.60 m = 0.00 V | 0.00 m = 2.56 V
Selects the polarity of the analog output so that
the maximum voltage selected using menu item
<f>
occurs at the maximum distance set using
menu item <e> or at 0.00 m as required.
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3. Making connections to the SF10
The SF10 gets power from either a regulated +5 V DC supply on the main connector or via the USB port when it is connected to a PC.
There are a number of digital and analog interfaces on the main connector and either one or a combination of interfaces may be
connected to a host controller. The built-in micro USB port can be used to input settings and to test the performance of the SF10.
Power supply option 1: USB
The SF10 can be powered directly from the USB port of a PC or laptop. This is particularly useful for testing the SF10 before it is
installed in your system and also for changing the settings in readiness for the final application.
Figure 3 :: Power from the USB port
Power supply option 2: Regulated +5 V DC
The second power supply option is to connect a regulated voltage of 5 V ± 10% DC to the main connector. If the power wires are more
than 30 cm long, we recommend using a decoupling capacitor, or other noise suppression components
to reduce the chance
interference being picked up on the power wires.
Figure 4 :: Regulated +5 V DC power supply connections
Communications using the USB port
The SF10 has a micro USB port that can be used to communicate with LightWare Terminal software on a PC. This connection also
provides power to the unit thereby presenting a quick way to test and configure the SF10. The LightWare Terminal software will
automatically detect the USB port that is connected to the SF10 and communications can be established by clicking on the
“Connect” icon. If more than one compatible device is present, click the “Laser” icon to select which USB port should be active.
Once communication has been established, settings can be changed by pressing the <SPACE>
key to access the menu and then
selecting the menu item that needs changing. Pressing the <SPACE>
key again restarts the measuring process. If no settings are
entered then the SF10 automatically restarts after two minutes. More details of the menu items are discussed in the “Menu options”
section below.
If you want to use a different serial emulation program then the USB serial protocol should be set to 115200 baud with 1 stop bit and
no parity or handshaking. All communications are in standard ASCII format.
Figure 5 :: USB communications
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Analog voltage interface
The analog interface on the main connector produces a linear voltage of between 0.00 V and 2.56 V that is proportional to the
measured altitude. The physical altitude in meters that equates to 2.56 V can be adjusted through the USB menu system. For
example, an altitude setting of 51.20 meters would produce a linear voltage output of 50 mV per meter.
Figure 6 :: Analog voltage connections
Serial interface
The serial interface on the main connector outputs the measured altitude in meters as an ASCII encoded number. This interface uses
3.3 V logic levels and can be connected directly to any similar, compatible interface. Distances are transmitted whenever the SF10
receives an ASCII character from the host controller. This character may have any value in the extended ASCII character set. The
baud rate for the serial interface is selectable through the USB menu system. The maximum delay between receiving a character and
returning the altitude is 25 ms.
Figure 7 :: Serial interface connections
I2C interface
The I2C interface on the main connector outputs a value that represents the altitude in centimetres. This interface operates in
“slave” mode and uses 3.3 V logic levels. The I2C address can be set through the USB menu system. The host controller acts as the
I2C “master” and sends the address to the SF10 as an 8 bit value (7 address bits plus 1 read bit). The SF10 then returns the altitude
as a 16 bit integer. The maximum delay between receiving the address and returning the altitude is 25 ms.
Figure 8 :: I2C interface connections
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4. Menu options
The SF10 can be connected through the on-board USB port to a Terminal emulation program running on a PC. The LightWare Terminal
software is available for download from www.lightware.co.za.
Once the USB connection is made, the Terminal window displays the distance reading from the SF10. Pressing the <SPACE> key stops
the measuring process and changes the display to a menu that lists all the available settings and configuration options. Pressing the
<SPACE> key again restarts the measuring process. If no changes are made, the unit will automatically begin to measure again after
two minutes.
Figure 9 :: LightWare Terminal showing menu options
a: Zero datum offset (-10.00 m … +10.00 m)
The point from which altitude measurements are taken can be adjusted using menu item <a>
. The range of values that can be
entered are from -10.00 meter to +10.00 meters and this value is subtracted from the altitude reading before it is made available on
any of the interfaces. The zero datum offset can be used to compensate for the mounting position of the SF10 in the airframe, where
distance readings may best be interpreted from a suitable point on the landing gear, rather than from the front face of the SF10.
b: Smooth output - Switches ON / OFF a data filter which smoothes the outputs
Menu item <b>
is used to reduce the effects of scrub, bushes and long grass on the mean altitude reading. Note that this filter
changes the time constant of the altitude measurements and therefore the rate of response.
c: Serial port baud rate (9600 … 115200)
The serial port transmits a serial string of ASCII encoded data from the SF10 to the host controller. The baud rate of transmission is
selected by menu item <c> and toggles through the standard baud rates from 9600 to 115200. By default, there is 1 stop bit and no
parity or handshaking on this serial port.
The ASCII string representing the altitude is in floating point format with two decimal places followed by carriage return and line
feed:
“22.48\r\n”
where carriage return and line feed are given by the hexadecimal ASCII characters:
\r = 0x0D
\n = 0x0A
The altitude is sent out of the serial port when any ASCII character is transmitted by the host controller to the SF10.
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d: I2C bus address (0x00 … 0x7F)
The I2C bus operates in slave mode and accepts an 8 bit address (7 address bits plus 1 read bit) before responding with a 16 bit,
binary coded integer that is the altitude in centimetres. The address can be set by selecting menu item <d> and is entered as a 7
bit, hexadecimal number.
e: Analog distance range (SF10/A: 1.00 m … 30.00 m, SF10/B: 1.00 m … 60.00 m & SF10/C: 1.00 m … 120.00 m)
The distance at which the maximum analog output of 2.56 V occurs can be set by selecting menu item <e>. The output voltage can
be converted back into a distance by using the formula:
a = v / 2.56 * c
where:
a = measured distance
v = voltage measured by the ADC of the host
c = 2.56 V distance setting
The analog voltage output updates 16 (SF10/C) or 32 (SF10/A and SF10/B) times per second and has a 12 bit resolution.
Figure 10 :: Altitude represented by distance (Serial / I2C) and analog voltage
f: Analog voltage range (0.00 V … 2.56 V or 0.00 V … 3.30 V)
Selects the maximum output voltage of the analog output - either 2.56 V or 3.30 V - by selecting menu item <f>.
g: Analog polarity (0.00 m = 0.00 V | 25.60 m = 2.56 V or 25.60 m = 0.00 V | 0.00 m = 2.56 V)
Selects the polarity of the analog output so that the maximum voltage selected using menu item <f> occurs at the maximum distance
set using menu item <e> or at 0.00 m as required.
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5. Instructions for safe use
The SF10 is a laser range finder that emits ionizing laser radiation. The level of the laser emission is Class 1M which indicates that
the laser beam is safe to look at with the unaided eye but must not be viewed using binoculars or other optical devices at a distance
of less than 15 meters. Notwithstanding the safety rating, avoid looking into the beam and switch the unit off when working in the
area.
CAUTION -- The use of optical instruments with this product will increase eye hazard.
The SF10 should not be disassembled or modified in any way. The laser eye safety rating depends on the mechanical integrity of the
optics and electronics so if these are damaged do not continue using the SF10. There are no user serviceable parts and maintenance
or repair must only be carried out by the manufacturer or a qualified service agent.
No regular maintenance is required for the SF10 but if the lenses start to collect dust then they may be wiped with suitable lens
cleaning materials. Make sure that the SF10 is switched OFF before looking into the lenses.
The SF10 should be mounted using the four holes provided in the circuit board. Do not hold or clamp the lens tubes as this may cause
damage and adversely affect the laser safety rating.
Laser radiation information and labels
Figure 11 :: Labelling on the SF10
Specification Value / AEL Notes
Laser wavelength 905 nm
Pulse width < 20 ns
Pulse frequency < 36 kHz
Peak power < 10 W 50 millimeter aperture at 2 meters
Average power < 0.6 mW 7 millimeter aperture
Average energy per pulse < 300 nj
NOHD 15 m Distance beyond which binoculars with may be used safely
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Appendix A :: Specifications
Appendix B :: Dimensions
Figure 12 :: Dimension drawings of the SF10
SF10/A (25 m) SF10/B (50 m) SF10/C (100 m)
Range 0 … 25 meters (natural targets) 0 … 50 meters (natural targets) 0 … 100 meters (natural targets)
Resolution 1 centimeter 1 centimeter 1 centimeter
Update rate 32 readings per second 32 readings per second 16 readings per second
Accuracy ±0.05 meter (70% reflective
target @ 20°C)
±0.05 meter (70% reflective
target @ 20°C)
±0.1 meter (70% reflective target
@ 20°C)
Power supply voltage 5.0 V ± 0.5 V DC 5.0 V ± 0.5 V DC 5.0 V ± 0.5 V DC
Power supply current 125 mA (maximum) 150 mA (maximum) 150 mA (maximum)
Outputs & interfaces Serial, I2C (up to 400 kHz) &
analog with maximum latency of
25 ms
Serial, I2C (up to 400 kHz) &
analog with maximum latency of
25 ms
Serial, I2C (up to 400 kHz) &
analog with maximum latency of
25 ms
Dimensions 30 x 56.5 x 50 millimeters 30 x 56.5 x 50 millimeters 30 x 56.5 x 50 millimeters
Weight 35 grams (excluding cables) 35 grams (excluding cables) 35 grams (excluding cables)
Connections Plug & socket, micro USB Plug & socket, micro USB Plug & socket, micro USB
Laser power 4 W (peak), 5 mW (average),
Class 1M
20 W (peak), <15 mW (average),
Class 1M
20 W (peak), <15 mW (average),
Class 1M
Optical aperture 51 millimeters 51 millimeters 51 millimeters
Beam divergence 0.4° 0.2° 0.2°
Operating temp. 0 ... 40°C 0 ... 40°C 0 ... 40°C
Approvals FDA accession number:
1630995-000 (2016/09)
FDA accession number:
1630995-000 (2016/09)
FDA accession number:
1630995-000 (2016/09)
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Appendix C :: Main cable type 1, 35 cm
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Appendix D :: Connecting to Pixhawk Autopilot using “serial 4”
Appendix E :: Electromagnetic interference (EMI) graphs
The SF10 family has been tested for radio frequency interference in accordance with MIL-STD-451C. The results are well within the
required limits so that neither direct radiation nor secondary radiation from wiring should cause interference to on-board systems
such as GPS and optical flow.
1. 14 kHz to 1 GHz - narrowband
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2. 14 kHz to 1 GHz - broadband
3. 1 GHz to 10 GHz - narrowband
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Revision history
Version Date Authors Comments
Rev 11 2016/09/14 TLP Updated FDA accession number “1630995-000 (2016/09)” in “Appendix A ::
Specifications” (page 11).
Rev 10 2016/03/07 TLP Update I2C feature “up to 400 kHz” in “Appendix A :: Specifications” (page 11).
Rev 9 2016/01/29 TLP Update FDA accession number “1410968-002 (2016/01)” in “Appendix A ::
Specifications” (page 11). Include “Appendix D :: Connecting to Pixhawk Autopilot
using “serial 4” (page 13).
Rev 8 2015/09/18 TLP Update FDA accession number “FDA: 1410968-001 (2015/09)” in “Appendix A ::
Specifications” (page 11). Added clarifications regarding the “I2C interface” 8 bit
value consisting of “7 address bits plus 1 read bit” (pages 7 & 9). Update “Figure 9 ::
LightWare Terminal showing menu options” (page 8). Updated menu option “c: Serial
port baud rate (9600 … 115200)” (pages 5 & 8). Updated menu option “d: I2C bus
address” (pages 5 & 9). Updated menu option “Analog 2.56 V distance” to “e: Analog
distance range” (pages 5 & 9). Include new menu item “f: Analog voltage
range” (pages 5 & 9). Include new menu item “g: Analog polarity” (pages 5 & 9).
Rev 7 2015/06/09 TLP Updated product part code “Main cable type 1, 35 cm” (page 12).
Rev 6 2015/01/26 TLP Updated value: I2C bus address is entered as an “8” bit, hexadecimal number (page
9). Include “Appendix C :: SF10 Communications cable assembly” (page 12). Include
“Appendix D :: Electromagnetic interference (EMI) graphs” (page 13).
Rev 5 2014/11/19 TLP Update product code references: “SF10/A” to “SF10/B (50 m)”; “SF10/B” to “SF10/C
(100 m)” and “SF10/C” to “SF10/A (25 m)”. Update “2. Quick start guide” software
menu item references for: “Ground offset” to “Zero datum offset”; “Altitude filter” to
“Smooth output”; and “Analog 2.56 V altitude” to “Analog 2.56 V distance” (page 5).
Amend “2. Quick start guide” I2C bus address to “0 … FF” (page 5). Update “a: Zero
datum offset” range from “0.00 m … +10.0 m” to “-10.00 m … +10.00 m” (page 5 & 8)
Include FDA accession number “FDA: 1410968-000 (2014/10)” in “Appendix A ::
Specifications” (page 11).
Rev 4 2014/09/30 TLP Include “Figure 2 :: Applications” (page 4).
Rev 3 2014/09/29 TLP
Include maximum range specifications and update rate for the SF10/B and SF10/C
modules (page 3). Updated “Summary of the settings” to include SF10/B model (page
4). Include information and specifications for SF10/B model (page 10).
Rev 2 2014/09/25 TLP
Include information and specifications for SF10/C model (page 10). Updated
references to “Damping” to “Altitude filter”. Update quick start settings table (page
4). Updated “Figure 8 :: LightWare Terminal showing menu options” (page 7). Update
“Appendix A :: Specifications” (page 10).
Rev 1 2014/08/25 TLP
Update reading rate to “32” per second (pages 1, 3, 8 & 10). Update accuracy
specification to “±0.04 meter (70% reflective target @ 20°C)” (page 10).
Rev 0 2014/07/12 JEP First edition
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